Remote grip optical fiber connector

ABSTRACT

An optical fiber connector comprises an outer housing configured to mate with a receptacle and a collar body disposed in the outer housing. The collar body receives and secures a ferrule in a first portion of the collar body. The ferrule includes a central bore that defines an axis. The ferrule further includes a fiber stub disposed in a portion of the central bore, the fiber stub comprising a first optical fiber having a first end proximate to an end face of the ferrule and a prepared second end terminating within the ferrule. The collar body further includes a second portion that includes a housing portion to house a gripping device that grips a second optical fiber.

BACKGROUND

1. Field of the Invention

The present invention is directed to an optical connector.

2. Related Art

Mechanical optical fiber connectors for the telecommunications industryare known. For example, LC, ST, FC, and SC optical connectors are widelyused.

However, commercially available optical connectors are not well suitedfor outside plant field installations. Typically, an adhesive isrequired to mount these types of ferrule-based connectors on to anoptical fiber. The process of bonding the fiber to the ferrule can beawkward and time consuming to perform in the field. Also post-assemblypolishing requires that the craftsman have a higher degree of skill.

Remote grip optical fiber connectors are also known, such as thosedescribed in U.S. Pat. No. 5,337,390. These connectors employ amechanical gripping element to secure the optical fiber as opposed to anadhesive.

Also known are hybrid optical splice connectors, as described in JPPatent No. 3445479, JP Application No. 2004-210251 (WO 2006/019516) andJP Application No. 2004-210357 (WO 2006/019515). However, these hybridsplice connectors are not compatible with standard connector formats andrequire significant piecewise assembly of the connector in the field.The handling and orientation of multiple small pieces of the connectorcan result in incorrect connector assembly that may either result indecreased performance or increase the chance of damaging the fiber.

Also known are connectors that incorporate fiber stubs that are factoryinstalled. In these connectors, the back end of the stub fiber ismechanically spliced to a field fiber, where an index matching gel isused to fill the gap between the back end of the fiber stub and thefront end of the terminated fiber. For example, see U.S. Pat. No.5,909,528. For outdoor applications, especially for environments thatcan undergo a wide temperature variation, the index of refraction of thegel may change as a function of temperature, leading to morereflections, thus limiting the connector performance in those particularapplications.

Another alternative includes the use of a fusion splice to connect afield fiber to a fiber stub. For example, see JP Application No.2004-317945. A fusion splice requires the use of expensive fusion splicemachines.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, an optical fiberconnector comprises an outer housing and a collar body disposed in theouter housing. The collar body receives and secures a ferrule in a firstportion of the collar body. The ferrule includes a central bore thatdefines an axis. The ferrule further includes a fiber stub disposed in aportion of the central bore, the fiber stub comprising a first opticalfiber having a first end proximate to an end face of the ferrule and aprepared second end terminating within the ferrule. The collar bodyfurther includes a second portion that includes a housing portion tohouse a gripping device that grips a second optical fiber.

In another aspect, the gripping device provides a contact force that isapplied to the second optical fiber in an axial direction and providesoptical contact with the second end of the first fiber inside thecentral bore.

In another aspect, the gripping device includes a gripping element andan actuating cap configured to engage the gripping element to secure asecond optical fiber disposed therein. In one aspect, the grippingelement comprises a ductile material having a focus hinge that couplestwo element legs, where the actuating cap includes a cam portion formedon a cap leg that engages a rear portion of collar body upon actuation,where each of the legs further includes slots formed at different axialpositions and oriented transverse to the axis. In another aspect, thegripping element further includes one or more projections located onopposite longitudinal end portions of the legs, wherein, upon actuationof the actuating cap, a first projection contacts a rear portion of theferrule and a second projection contacts a portion of the actuating cap.In one aspect, the contact force is from about 0.1 lbs. to about 0.4lbs.

In another aspect, the actuating cap includes a cover portion and a mainbody portion that includes two main legs and two spring legs, whereinthe main legs include cams disposed on inner surfaces thereof to engageand clamp the element about the second optical fiber when the cap ispressed onto the element during actuation. In one aspect, the main legseach include a forward shoulder portion to engage with a retaining wallportion of the collar body disposed between the gripping element and theferrule. During actuation, the spring legs engage with a cam surface ofan opposite portion of the collar body.

In another aspect, the ferrule includes a cut-out portion positioned ata generally midpoint axial location of the ferrule that provides alocation to apply an adhesive to the central bore at a first portion ofthe ferrule.

In another aspect, the ferrule includes a slot formed generallytransverse to the axis that receives at least one of a cleaning materialand a polishing material that is applicable at least one of to thesecond end of the first fiber and an abutting end of the second fiber.In one aspect, the slot is oriented at an angle of about 5°-about 10°from normal to the axis.

In another aspect, the ferrule includes a through-hole intersecting andformed generally transverse to the central bore that receives at leastone of a cleaning material and a polishing material that is applicableto at least one of the second end of the first fiber and an abutting endof the second fiber. In another aspect, the optical fiber connectorfurther comprises a cable holding member that includes a cable clampingmechanism disposable therein. In one aspect, the cable holding memberfurther includes a main body and a retention clip, where the retentionclip is configured to engage a portion of the main body of the cableholding member and secure the clamping mechanism, and where the clampingmechanism includes a receptive groove formed therein having engagingprojections configured to securely retain the outer portion of a fibercable that houses the second optical fiber.

In another aspect, the connector is configured as one of a plug-typeconnector and a socket-type connector. In one aspect, the outer housingis configured to mate with a receptacle.

According to another aspect of the present invention, an optical fiberconnector comprises an outer housing and a collar body disposed in theouter housing. The collar body includes a flexible wall portion, wherethe collar body receives and secures a ferrule in a first portion of thecollar body, where the ferrule includes a central bore that defines anaxis. The ferrule further includes a fiber stub disposed in a portion ofthe central bore, the fiber stub comprising a first optical fiber havinga first end proximate to an end face of the ferrule and a preparedsecond end terminating within the ferrule. The collar body furtherincludes a second portion that includes a housing portion to house agripping device that grips a second optical fiber, where the first andsecond fibers are optically coupled upon connection of the optical fiberconnector to one of a connector coupling, a connector adapter and aconnector socket.

In another aspect, the flexible wall portion of the collar bodycomprises bowed outer side walls. In another aspect, the flexible wallportion of the collar body comprises a resilient material forming aportion of the side walls.

The above summary of the present invention is not intended to describeeach illustrated embodiment or every implementation of the presentinvention. The figures and the detailed description that follows moreparticularly exemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further described with reference to theaccompanying drawings, wherein:

FIG. 1 is an isometric view of an exemplary optical connector accordingto an aspect of the present invention.

FIG. 2 is an isometric cut-out view of the exemplary optical connectorof FIG. 1.

FIG. 3 is an isometric cut-out close-up view of several components ofthe exemplary optical connector of FIG. 1.

FIG. 4 is an isometric close-up view of a gripping element according toan aspect of the present invention.

FIG. 5 is a side view of the gripping element of FIG. 4.

FIG. 6 is a side view of several components of the exemplary opticalconnector of FIG. 1.

FIG. 7 is a close-up side view of the gripping element of an aspect ofthe present invention prior to actuation.

FIG. 8 is a close-up side view of the gripping element of an aspect ofthe present invention after actuation.

FIG. 9 is a side view of another exemplary optical connector accordingto an alternative aspect of the present invention.

FIG. 10 is a side view of another exemplary optical connector accordingto an alternative aspect of the present invention.

FIG. 11 is an isometric view of several components of an opticalconnector according to an alternative aspect of the present invention.

FIG. 12 is an isometric view of several components of an opticalconnector according to an alternative aspect of the present invention.

FIG. 13 is an isometric cut-out view of several components of an opticalconnector according to an alternative aspect of the present invention.

FIG. 14 is a side view of several components of an optical connectoraccording to an alternative aspect of the present invention.

FIG. 15 is an exploded view of an optical connector according to analternative aspect of the present invention.

FIG. 16 is a top view of an exemplary ferrule according to anotheralternative aspect of the present invention.

FIG. 17 is a top view of an exemplary ferrule according to anotheralternative aspect of the present invention.

FIG. 18 is an isometric view of an exemplary ferrule according toanother alternative aspect of the present invention.

FIG. 19 is an isometric view of an exemplary ferrule according toanother alternative aspect of the present invention.

FIG. 20 is an isometric view of another exemplary ferrule according toanother alternative aspect of the present invention.

FIG. 21 is an isometric view of another exemplary ferrule according toanother alternative aspect of the present invention.

FIG. 22 is an exploded view of another exemplary optical connectoraccording to another alternative aspect of the present invention.

FIGS. 23-25 show schematic top views of another exemplary opticalconnector during connection according to another alternative aspect ofthe present invention.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following Detailed Description, reference is made to theaccompanying drawings, which form a part hereof, and in which is shownby way of illustration specific embodiments in which the invention maybe practiced. In this regard, directional terminology, such as “top,”“bottom,” “front,” “back,” “leading,” “forward,” “trailing,” etc., isused with reference to the orientation of the Figure(s) being described.Because components of embodiments of the present invention can bepositioned in a number of different orientations, the directionalterminology is used for purposes of illustration and is in no waylimiting. It is to be understood that other embodiments may be utilizedand structural or logical changes may be made without departing from thescope of the present invention. The following detailed description,therefore, is not to be taken in a limiting sense, and the scope of thepresent invention is defined by the appended claims.

The present invention is directed to an optical connector. Inparticular, the optical connector of the exemplary embodiments providesa fiber stub-type connector without the need for fusion splicing orindex matching gel, as the stub fiber and field fiber are held inphysical contact during optical connection of the connector. Theconnector structure includes a gripping device that provides acontrolled contact force to a field fiber that is terminated to thefiber stub. This contact force can be maintained over a wide temperaturevariation. The exemplary connector can be field terminated without theneed for extensive field polishing.

In particular, as shown in the embodiments below, an exemplary opticalfiber connector comprises an outer housing configured to mate with areceptacle and a collar body disposed in the outer housing. The collarbody receives and secures a ferrule in a first portion of the collarbody, where the ferrule includes a central bore that defines an axis. Afiber stub is disposed in a portion of the central bore, with the firstend being proximate to an end face of the ferrule and a prepared secondend terminates within the ferrule. The collar body can house a grippingdevice that provides a contact force that is applied to a second opticalfiber in the axial direction that contacts with the second end of thefirst fiber inside the central bore.

According to a first exemplary embodiment, an optical fiber connector100 is shown in isometric view in FIG. 1. FIGS. 2-8 provide moredetailed views of various components of optical connector 100.

As shown in FIG. 1, exemplary optical connector 100 includes a body 112,a ferrule 114 provided at the body 112, and an incorporated opticalfiber (see fiber 117 in FIG. 2) of a predetermined length securelysupported at the ferrule 114. The optical connector 100 also includes agripping device 118 provided at the body 112 near the ferrule 114 thatoperates to securely support terminated field optical fiber 116 (seeFIG. 2) from an optical fiber cable 101. A cable holding member 120 isprovided at the body at an opposite side to the ferrule 114 from thegripping device 118 and is configured to hold optical fiber cable 101via a clamping mechanism 121. In a preferred aspect, field fiber 116 isspliced to stub fiber 117 in the ferrule 114 of the connector 100through a butt couple. No index matching gel is required at thejoint/splice location, as appropriate contact force between the fibersis maintained through the structure of the gripping device, as isdescribed in further detail below.

The body 112 can include a hollow inner cylinder or collar body 125 (seeFIGS. 2 and 6) in which the ferrule 114 is secured (via an adhesive orinterference fit) and a hollow outer housing 124 that accommodates theinner cylinder 125 slidably in an axial direction.

The collar body 125 and the outer housing 124 can both be formedintegrally from a suitable plastic material, such as Vectra, by, forexample injection molding, although metal and other suitably rigidmaterials can also be utilized. Collar body 125 can slide and can beforcibly held forward by action of a resilient element, such as aresilient element 129, which acts on rear collar body portion 128, inthe body of connector. Alternatively, a spring element (not shown) canbe utilized to provide forward force. In a preferred aspect, the outerhousing 124 is configured to be received by a receptacle, for example, aFAS socket receptacle or a FA socket receptacle, both of which areavailable from 3M Company, St. Paul, Minn.). Alternatively, opticalconnector 100 can be configured to mate with a standard formatreceptacle, such as SC, ST, FC, and LC connector formats. As would beapparent to one of skill in the art given the present description, theoptical connectors described herein can be employed in both plug-typeconnectors and socket-type connectors.

The collar body 125 can be formed of a stepped tubular shaped memberhaving a center axis coincident with the fiber axis 102. An outerdiameter front portion 126 and an outer diameter rear portion 128 areintegrally formed adjoining each other in the axial direction. The frontportion 126 is open at its front end in the axial direction and isformed with a first recess securely receiving the ferrule 114.

The outer housing 124 of the body 112 is provided with a first cavityopening 146 a at the front end in the axial direction (left end in thefigure). The first cavity 146 a of the outer housing 124 receives thearea of the front end 126 of the collar body 125 which holds the ferrule114. An opening 146 b is also provided to receive gripping device 118,which is disposed in a housing area of the collar body. The collar body125 has an opening that receives the gripping device 118 which caninclude a gripping element 142 and a cap 144. The outer housing 124 hasan opening that is aligned with the opening 146 b in the collar bodythat allows access to the cap 144 to move from an unactuated position toan actuated position.

The gripping device 118 can float in the housing area. For example, aspring element (no shown) can be used to hold the element 142 in opening146 such that the element rests on the bottom of the opening and againstthe back wall of the opening 146 b. Also, the spring can allow for theelement to expand and contract as temperature changes. The rear portionof the collar body can accommodate a coil spring (not shown) for endloading of the ferrule to appropriate load levels.

The ferrule 114 of the optical connector 100 is a generally tubularmember formed with a precision bore or through-hole (also referred to asa fiber holding channel) along its center axis for holding fiber 117 andhas a substantially cylindrical outer surface. The central bore orthrough-hole guides and aligns a field fiber (fiber 116) to make anoptical connection with fiber 117. The ferrule 114 is provided with anabutting end face 162 at one end in the axial direction extending flatsubstantially perpendicular to the center axis. The central bore isgenerally centered on the end face 162 and extends straight along thecenter axis. In a preferred aspect, the ferrule end face 162 is tapered.Also, the central bore can have a tapered guide surface 164 at theopposite side from the end face 162 (see FIG. 3). The ferrule 114 can befabricated from a ceramic, a glass, a plastic, or other conventionalmaterial.

The fiber holding channel of the ferrule 114 includes fiber 117 (alsoreferred to as a fiber stub) having a predetermined length inserted init and secured by an adhesive (not shown). In addition, the ferrule 114can include a ferrule cut-out portion or slot 115 (positioned at agenerally midpoint location) that provides a location to monitor theapplication of the adhesive. In other embodiments, the ferrule slot canalso provide access to the fiber joint location and for cleaning theabutting ends of fibers 117 and 116.

In a preferred aspect, the predetermined length of fiber 117 is lessthan the length of the ferrule (see e.g., FIG. 3). In this aspect,optical fiber 117 includes finished (e.g., polished) end faces, wherethe finishing process takes place at the factory. In one aspect, thesecond (rear) end of fiber 117 can be polished in the factory to reducethe sharpness of the edge of the fiber. For example, an electrical arc,such as one provided by a conventional fusion splicer machine, can beutilized to melt the tip of the fiber and form a rounded end, therebyremoving the sharp edges. This electrical arc technique can be used inconjunction with polishing by an abrasive material to better control endface shape while reducing possible distortion of the core. Analternative non-contact method utilizes laser energy to ablate/melt thetip of the fiber.

Fiber 117 (and field fiber 116) can comprise a standard single mode ormultimode optical fiber, such as SMF 28 (available from Corning Inc.).In an alternative embodiment, fiber 117 can additionally include acarbon coating disposed on the outer clad of the fiber to furtherprotect the glass-based fiber.

In an exemplary aspect, fiber 117 can be secured in ferrule 114 asfollows. An adhesive is injected into the central bore of the ferrule.Preferably, the adhesive is applied at the forward end of the slot 115(the forward end is closer to the ferrule end face) so that adhesivewill not flow into the rear portion of the ferrule (i.e., nearest thegripping device 118). In a preferred aspect, the slot 115 has a depth toa surface of the central bore that helps reduce the possibility ofadhesive flowing toward the gripping device side of the ferrule. Theadhesive, such as an epoxy, is preferably designed to withstand largetemperature variations, such as the standard Telcordia 326 range of fromabout −40° C. to about 75° C., or a range from about −40° C. to about85° C. A fiber 117 having first and second ends that are prepared (e.g.,polished, radiused, beveled, prepared as described above or otherwiseprepared in a conventional manner) is inserted in the ferrule centralbore at the tapered end 164 and fed through until a portion of the fiber117 protrudes beyond the ferrule end face 162. The fiber 117 can befurther pulled from the front end until the back end of the fiber 117 ispositioned within the central bore of the ferrule by a predeterminedamount. The fiber is then bonded in the ferrule by the injectedadhesive. The excess length of fiber protruding from the ferrule endface 162 is removed. The exposed fiber end face (located at about theferrule end face) is then polished flush with the ferrule end face 162using a conventional polishing technique. Thus, ferrule 114 can includea stub fiber having a polished end face at the ferrule end face and aprepared second end located within the ferrule at or about fiber jointlocation 119 (see FIG. 3). In an alternative aspect (not shown) theabutting ends of the fibers 117 and 116 can contact one another withinthe area of slot 115. In that respect, visual inspection of the fiberjoint may be made in a straightforward manner.

As mentioned above, the optical connector 100 also includes a grippingdevice. The preferred aspects describe a gripping device 118 thatincludes a gripping element and actuating cap. Alternatively, thegripping device can have a design similar to that of a conventionalmechanical splice currently available in the industry, such as describedin Japan Patent Kokai H9-318836. For example, in an alternative aspect,the gripping device can include a wedge-actuated mechanical grippingelement. Other variations can be utilized as would be apparent to one ofskill in the art given the present description. In a preferred aspect,gripping device 118 of the optical connector 100 comprises a fibersecuring or gripping element 142 disposed in a second recess of thecollar body 125. The gripping element grips an optical fiber to beterminated in the field (here, field fiber 116). The gripping device 118can also include an actuating cap to actuate the fiber gripping element142. In a preferred aspect, the gripping element 142 comprises a sheetof ductile material having a focus hinge 142 a that couples two legs 142b and 142 c (see FIG. 4), where one or both of the legs can include afiber gripping channel (e.g., a V-type (or similar) groove 147 (see FIG.5)) to optimize clamping forces for a conventional glass optical fiber(fiber 116) received therein. The ductile material, for example, can bealuminum or anodized aluminum, or another malleable material. Grippingdevice 118 allows a field technician to remotely (from the ferrule) gripthe optical fiber 116 being terminated with the fiber stub 117. Fieldfiber 116 is stripped of its outer jacket and buffer coating near theabutting end. In a preferred aspect, the abutting end of fiber 116 canalso be cleaved (flat or angled, with or without bevels) using a fieldfiber cleaver and cleaving process.

In addition, the gripping element 142 includes two openings or slotsformed in each of the element legs oriented transverse to the directionof the fiber axis. For example, as shown in FIG. 4, slots 143 a and 143b are formed in leg 142 c. Slots of similar configuration are alsoformed in leg 142 b. These slots are preferably positioned at differentlongitudinal locations relative to the front and rear ends of theelement 142. In this manner, the slots can generate different springforces that are applied by the element 142 in the axial direction. Forexample, as shown in FIG. 4, a first spring beam 145 a is provided atthe front portion of the element 142 (i.e., closest to the ferrule) anda second spring beam 145 b is provided at the rear portion of theelement 142. In one aspect, spring beam 145 a has a weaker springconstant than spring beam 145 b. The slots 143 a, 143 b are preferablyformed so that the slots may cut across the fiber guiding groove 147(see FIG. 5). The gripping element 142 can also include projectionslocated on longitudinal end portions of the legs. For example, FIG. 4shows projections 143 c and 143 d formed on element leg 142 c. In apreferred aspect, projection 143 c can contact a rear portion of ferrule114 and projection 143 d can contact a portion of actuating cap 144.This flexible gripping element structure can distribute an appropriateaxial force so that sufficient contact between fiber 116 and stub fiber117 is maintained.

In an exemplary embodiment, the gripping device 118 is mountable in thecollar body 125 such that it is substantially secured within a fixedelement cradle or nest formed within portion the collar body 124.Actuating cap 144 is configured to engage the gripping element 142 suchthat the element 142 grips the fiber 116 inserted therein. The cap 144can be formed or molded from a polymer material, although metal andother suitable materials can also be utilized. In one aspect, the cap144 can be formed from a material being the same as the material formingthe element 142. Alternatively, a material having at least a similarcoefficient of thermal expansion (CTE) as the element can be utilized.FIG. 7 shows a schematic side view of exemplary gripping device 118before actuation of the element 142 that grips field fiber 116. FIG. 8shows a schematic side view of the gripping device 118 after actuationof the element 142 by cap 144. In this exemplary aspect, the actuationprocedure also axially moves element 142 (and the fiber gripped therein)towards the ferrule to provide an appropriate contact force for fiber116 to optically couple to stub fiber 117.

In operation, as the cap 144 is moved from an open position (FIG. 7) toa closed position (downward in the direction of arrow 103 in FIG. 8),one or more cam bars located on an interior portion of the cap 144 canslide over the element legs 142 b and 142 c, urging them toward oneanother. The glass portion of the fiber 116, placed in the groove 147formed in the element 142, is gripped as the element legs are movedtoward one another by the cap 144. Also, a cam portion 144 a formed oncap leg 144 b contacts the rear portion 125 a of collar body 125 andanother portion of leg 144 b contacts protrusion 143 d of the element.As the cap 144 is further moved downward, cam 144 a engages surface 125b of the collar body 125. Some resistance to forward motion is providedby the forward spring beam, as protrusion 143 c contacts a portion offerrule 114. As the (rear) spring beam 145 b provides a stronger springforce than the spring force of (forward) spring beam 145 a, the element142 is urged in the direction of arrow 102 (towards the ferrule 114)under a controlled force. For example, a net spring force of about 0.1lbs. to about 0.4 lbs. can provide a suitable pre-load for the fiberjoint. As shown in FIG. 8, the abutting end 116 a of fiber 116 istranslated within the ferrule 114 towards stub fiber 117. The forcecreates and maintains good optical contact between the fibers in theferrule 114. In addition, at higher temperatures, ferrule 114 can expandand act against the projection 143 c, as this force would be absorbed byspring beam 145 a. Also, the collar body can act against projection 143d, but this force would be absorbed by spring beam 145 b, with the netforce kept within the preferred range of about 0.1 lbs. to about 0.4lbs. At lower temperatures, the ferrule may contract, but spring beams145 a and 145 b can compensate for the created gap. Referring back toFIG. 1, connector 100 further includes a cable holding member 120. Therear portion of the cable holding member can include a receptive groovefor receiving the optical fiber cable 101. In a preferred aspect, theoptical fiber cable can include a conventional 250 μm disposed in acenter portion of an outer jacket, which has a rectangular shape in thisexemplary aspect. The cable holding member can secure the optical fibercable 101 to prevent axial strain on the fiber 116 being joined to thestub fiber 117 in the ferrule. The structure of the cable holding member120 and the clamping mechanism 121 are described in more detail belowwith respect to the embodiment shown in FIG. 15.

An alternative aspect of the present invention is shown in FIGS. 9-15,where a connector 200 includes a gripping device 218 that has analternative construction (as compared to gripping device 118 describedabove). Exemplary optical connector 200 includes a body 212, a ferrule214 provided at the body 212, and a fiber stub 217 of a predeterminedlength securely supported at the ferrule 214. The optical connector 200also includes gripping device 218 to securely support terminated fieldoptical fiber 216 (see FIG. 15) from an optical fiber cable 201. A cableholding member 220 is provided at the body at an opposite side to theferrule 214 from the gripping device 218 and is configured to holdoptical fiber cable 201 via a clamping mechanism 221. In a preferredaspect, field fiber 216 is spliced to stub fiber 217 in the ferrule 214of the connector 200 through a butt couple at joint location 219. Noindex matching gel is required at the joint/splice location, asappropriate contact force between the fibers is maintained through thestructure of the gripping device.

The body 212 can include a hollow inner cylinder or collar body 225 (seeFIGS. 12-14). The ferrule 214 may be secured in a front portion of thecollar body by an adhesive or interference fit. A hollow outer housing224 receives the collar body 225 slidably in an axial direction. Thecollar body 225 and the outer housing 224 can both be formed integrallyfrom a suitable plastic material by, for example injection molding,although metal and other suitably rigid materials can also be utilized.In a preferred aspect, the outer housing 224 is configured to bereceived by a mating receptacle, for example, a FAS socket receptacle ora FA socket receptacle, both of which are available from 3M Company, St.Paul, Minn.). Alternatively, optical connector 200 can be configured tomate with a standard format receptacle, such as SC, ST, FC, and LCconnector formats. The collar body 225 can include a stepped, tubularshaped member having a center axis coincident with the fiber axis 202.The front portion 226 of the collar body 225 is open at its front end inthe axial direction and is formed with a first recess 225 a thatsecurely receives the ferrule 214.

The outer housing 224 of the body 212 is provided with a first cavityopening at the front end in the axial direction (left end in thefigure). The first cavity of the outer housing receives the area of thefront end 226 of the collar body 225. An opening 246 b is also providedto receive gripping device 218 in a housing area formed in the collarbody (see area 225 b shown in FIG. 12).

The ferrule 214 of the optical connector 200 is a generally tubularmember formed with a precision bore or through-hole along its centeraxis for holding fiber 217 and has a substantially cylindrical outersurface. The bore or through-hole guides and aligns a field fiber (fiber216) to make an optical connection with stub fiber 217. The ferrule 214is provided with an abutting end face 262 at one end in the axialdirection extending flat substantially perpendicular to the center axisand the precision bore has an opening at the center of the end face 262and extends straight along the center axis. In a preferred aspect, theferrule end face 262 is angled or tapered. The ferrule 214 can befabricated from a ceramic, a glass, a plastic, or other conventionalmaterial.

In addition, the ferrule 214 can include a ferrule slot 215 thatprovides a location to monitor the application of an adhesive in theferrule to secure the fiber stub. The stub fiber 217 has a predeterminedlength and is secured by an adhesive (not shown) in the central bore orthrough-hole. Optical fiber 217 includes finished (e.g., polished) endfaces, where the finishing process takes place at the factory, as isdescribed above with respect to connector 200. Fibers 217 and 216 cancomprise a standard single mode or multimode optical fiber, such as SMF28 (available from Corning Inc.). Fiber 217 can be secured in ferrule214 in a manner the same as or similar to that described above withrespect to connector 100. Thus, ferrule 214 can include a stub fiberhaving a polished end face at the ferrule end face and a prepared secondend located within the ferrule 214 at or about joint location 219 (seeFIG. 13). In a preferred aspect, the abutting end of fiber 216 can becleaved (flat or angled, with or without bevels) using a field fibercleaver and cleaving process.

In a preferred aspect, the gripping device 218 of the optical connector200 comprises a fiber securing or gripping element 242 disposed in ahousing area 225 b of the collar body. Element 242 grips an opticalfiber 216 that is to be terminated to the stub fiber 217. The grippingdevice 218 also includes an actuating cap 244 to actuate the fibergripping element 242. In a preferred aspect, the gripping element 242comprises a sheet of ductile material having a focus hinge that couplestwo legs, where each of the legs includes a fiber gripping channel(e.g., a V-type (or similar) groove 247 (see FIG. 13)) to optimizeclamping forces for a conventional glass optical fiber (fiber 216)received therein. The ductile material, for example, can be aluminum oranodized aluminum, or another malleable material. In this exemplaryaspect, element 242 does not include slots to generate different axialspring forces. It is noted that the element 242 of this exemplaryembodiment is not required to include slots formed therein to generatedifferent spring beams.

Actuating cap 244 is configured to engage the gripping element 242 suchthat the element 242 grips the fiber 216 inserted therein. The cap 244can be formed or molded from a polymer material, although metal andother suitable materials can also be utilized. In particular, actuatingcap 244 includes a cover portion 244 e (contacted by a technician oractuating device during actuation) and a main body portion 244 f. Themain body portion 244 f includes two main legs 244 c and 244 d and twospring legs 244 a and 244 b. The main legs 244 c and 244 d include camsdisposed on inner surfaces to engage and clamp the legs of element 242when the cap is pressed onto the element 242. Further, the main legs 244c and 244 d can each include a forward shoulder portion (e.g., shoulderportions 244 h and 244 i shown in FIG. 12) designed to engage with aretaining wall portion 225 d of the collar body 225 disposed between thegripping element and the ferrule 214.

The spring legs 244 a and 244 b are configured to engage with a camsurface 225 a of the rear portion of the collar body 225. During thisengagement, the spring force generated by the contact of legs 244 a and244 b will urge the cap/element forward, and the field fiber 216 grippedtherein, towards the ferrule. The structure of spring legs 244 a and 244b (providing a forward axial force) and the shoulder portions 244 h and244 i of the main legs (providing a rearward axial force) can provide acontrolled total contact force so that sufficient contact between fiber216 and stub fiber 217 is maintained in ferrule 214 after termination.For example, a pre-load force of about 0.1 lbs. to about 0.4 lbs. canprovide a suitable pre-load for fiber 216 at the fiber joint.

Also, the above connector design can address temperature fluctuationsthrough the above-mentioned spring leg action. The spring provides thedesired force throughout the temperature range. For example, at hightemperatures, the collar body and cap (or gripping device 218) canexpand, but spring leg(s) 244 a, 244 b can engage with cam surface 225 aat the rear portion of the collar body. Here, the spring legs 244 a, 244b can maintain adequate spring force on the element to ensure good fiberto fiber contact despite a CTE mismatch between collar and capmaterials. Similarly, at low temperatures when the collar and capcontract, the spring force can compensate for a created gap.

Referring to FIG. 15, connector 200 further includes a cable holdingmember 220 that includes a cable clamping mechanism 221 having a mainbody, a lid 221 a and a retention clip 221 b. The clip 221 b isconfigured to engage a portion of the main body of the cable holdingmember 220 and secures the clamping mechanism 221 therein, whereas lid221 a can trap the cable into mechanism 221 and slidably move into cableholding member 220 before engagement by clip 221 b. Clamping mechanism221 includes a receptive groove formed therein having engagingprojections (such as rib structures or teeth) formed on one or moreinner walls that are configured to securely retain the outer portion ofcable 201. In one exemplary aspect, the projections have a saw-toothshape in cross-section and are arranged so as to bite into the sheath ofthe optical fiber cable 201 received in the receptive groove at theirtop areas and statically hold the optical fiber cable in the receptivegroove. In particular, by forming the plurality of engaging projectionsin saw-tooth shapes having the above orientations, the cable holdingmember 220 can strongly prevent the optical fiber cable received in thereceptive groove from being easily pulled out of the connector.

In a preferred aspect, the central axis of the cable holding member 220coincides with the fiber axis. The main body of member 220 can beconfigured to slidably engage the outer body portion 224 of body 212.Overall retention can be achieved by a latch mechanism, such as by latch231 of body 212 engaging with notch or opening 232 of the cable holdingmember body. The cable holding member 220 can be formed integrally froma suitable plastic material by for example injection molding, or from asuitably rigid material.

In an exemplary aspect, a field termination process is provided asfollows. A field fiber (e.g., fiber 116, 216) can be inserted into thecable clamp assembly (e.g., 120, 220). The fiber end can be prepared bye.g., cutting, stripping, and cleaving (flat or angled). The preparedfiber end is then inserted into the collar body/housing, through anunactuated gripping device, until the terminal end of the field fiberbutts against the second end of the fiber stub (e.g., 117, 217), duringwhich a fiber bow may be created. The actuating cap (e.g., 144, 244) ofthe gripping element can be pressed down onto the gripping element(e.g., 142, 242) to actuate the gripping of the field fiber and theproper load can be applied to the field fiber for sufficient contact tothe fiber stub. After actuation, the fiber bow may be released and thecable may be held in place by the cable clamp assembly 220.

In an alternative embodiment, a collar body having an alternativestructure can be utilized. For example, the collar body can be designedwith one or more flexible outer walls that will bow outwards when theferrule is subjected to a compression force. This structure can providefor additional contact force between the fiber stub and the field fiber.Also, this structure can be utilized to provide a safety interlock tooptically decouple the fiber joint when the connector is not in use.This alternative embodiment is described in further detail below.

In a further alternative embodiment, the exemplary fiber connectorsdescribed herein can include an alternative ferrule structure. Forexample, FIGS. 16-19 show various views of a ferrule 314 that includesan access slot 313 for polishing/cleaning the abutting fiber ends offibers 317 and 316. The access slot 313 can be made with a saw cut andcan be oriented generally transverse to the central bore of the ferrule314. For example, the slot 313 may be oriented at a small angle (e.g.,about 5°-10° from normal to the fiber axis) for cleaning/polishingangle-cleaved/polished fibers. This small angle can be utilized tooptimize reflection performance. In a preferred aspect, the slot 313passes completely through the fiber pathway and can have a width fromabout 0.005″ to about 0.060″. The ferrule 314 can be fabricated from aceramic, a glass, a plastic, or other conventional material. In apreferred aspect, fiber slot 313 is positioned at the location of thefiber joint 319, where fibers 317 and 316 are butt coupled. Fibers 317and 316 can be constructed the same as or similar to the fibersdescribed above.

In particular, fiber stub 317 can be installed in a manner similar tofiber 117 described above. A polishing or cleaning material 360 in stripform can be placed in slot 313 prior to insertion of the field fiber316, whose abutting end can be cleaved (flat or angled, with or withoutbevels) using a field fiber cleaver and cleaving process. The fieldfiber can then be inserted such that the polishing or cleaning material360 is disposed between the abutting ends of fibers 317 and 316. Thepolishing or cleaning material 360 can remove debris that may be pickedup by the abutting ends during the installation process. In particular,the abutting fiber ends can be cleaned by pulling a tab portion of thepolishing or cleaning material 360 to remove the strip. As the strip isremoved, it contacts both abutting fiber end faces. The gripping devicecan be actuated prior to or after the polishing process. In a preferredaspect, the polishing or cleaning material 360 can comprise a polishingribbon tape, and/or other cleaning materials such as nonwoven materials,lint free materials, abrasives, adhesives, alcohol or HFE wipes disposedon either or both of the strip faces.

In a further alternative embodiment, an alternative ferrule 414 is shownin FIGS. 20 and 21. Ferrule 414 can be constructed similar to ferrule314, except that access to the fiber joint area 419 is provided by athrough-hole 413 disposed generally transverse to the central bore ofthe ferrule. The polishing or cleaning material used in conjunction withthis aspect can be shaped in a string or floss-like form, such as apolyimide thread (e.g., Kevlar), that can be inserted and removedthrough the through-hole 413. As mentioned above, an alternativestructure can be utilized to provide a safety interlock such that thefiber joint between the stub fiber and the field fiber is opticallydecoupled when the connector is not in use. In this alternative aspect,an exemplary optical fiber connector 500 is shown in FIGS. 22-25.Optical connector 500 is configured to mate with a receptacle. Forexample the exemplary optical connector 500 can be configured as havingan SC, ST, FC, or LC connector format.

Optical fiber connector 500 can include a connector body having ahousing shell 512 that is configured to be received in a receptacle(e.g., an SC coupling, an SC adapter, or an SC socket), and a backbone516 that is housed inside the shell 512 and that provides structuralsupport for the connector 500. In addition, backbone 516 furtherincludes at least one access opening 517, which can provide access toactuate a gripping device disposed within the connector. Backbone 516can further include a mounting structure 518 that provides for couplingto a fiber boot 580, which can be utilized to protect the field fiberfrom bend related stress losses. According to an exemplary embodiment ofthe present invention, shell 512 and backbone 516 can be formed ormolded from a polymer material, although metal and other suitably rigidmaterials can also be utilized. Shell 512 is preferably secured to anouter surface of backbone 516 via snap fit.

Connector 500 further includes a collar body 520 that is disposed withinthe connector housing and retained therein. The collar body 520 is amulti-purpose element that can house a gripping device 540 and a fiberbuffer clamp. The collar body also includes a flexible wall structure,such as bowed outer or side walls 527. The bowed side walls 527 areflexible and can provide axial movement to the ferrule 532, which isfirmly seated against the internal flange 521 a of the collar body. Inan alternative aspect, the outer walls of the collar body can include aportion thereof having a compliant material to provide flexibility.

The collar body can be configured to have some limited axial movementwithin backbone 516. For example, the collar body 520 can include ashoulder 525 that can be used as a flange to provide resistance againsta spring 555, interposed between the collar body and the backbone, whenthe ferrule 532 is inserted in, e.g., a receptacle. According to anexemplary embodiment of the present invention, collar body 520 can beformed or molded from a polymer material, although metal and othersuitable materials can also be utilized. For example, collar body 520can comprise an injection-molded, integral material. The choice ofsuitable materials for the collar body can be made in accordance withtemperature stability parameters, as discussed in pending application(Attorney Docket No. 62902US002), incorporated by reference discussedherein.

Structurally, collar body 520 includes a first end portion 521 having anopening to receive and house a ferrule 532. Ferrule 532 can be formedfrom a ceramic, glass, plastic, or metal material to support the opticalfiber being inserted and terminated. In a first exemplary aspect,ferrule 532 is a ceramic ferrule. Ferrule 532 can include a stub fiber504 (similar to stub fibers 117 and 217 described above). In addition,ferrule 532 can include a first ferrule slot (similar to slots 115 and215 described above) to apply and monitor a bonding adhesive and/or asecond ferrule slot (configured in a similar manner to slot 313described above or through-hole 413). The stub fiber and the field fibercan comprise a standard single mode or multimode optical fiber, such asSMF 28 (available from Corning Inc.). Ferrule 532 is preferably disposedflush with flange portion 521 a and secured within the collar bodyportion via an epoxy or other suitable adhesive. Alternatively, ferrule532 may be friction fit in the first end portion 521 of the collar body520, such as being fitted and secured against flange portion 521 a.

Collar body 520 further includes a housing portion 523 that provides anopening 522 in which the gripping device 540 can be inserted in thecentral cavity of collar body 520. In an exemplary aspect, the grippingdevice 540 can include an element 542 and an actuating cap 544. Grippingelement 542 is mountable in the housing portion 523 of collar body 520such that it is substantially secured within a fixed element cradle ornest 543 formed within the housing portion. When the element 542 isplaced in the cradle or nest 543, a portion of the element is registeredagainst a rear wall 523 a of the housing portion 523. The other end ofelement 542 is disposed against elastic element 529, such as a springarm. The axial force provided by spring arm 529 can be selected based onthe intended force distribution within the connector over the expectedtemperature range of operation.

In a preferred aspect, the gripping element 542 comprises a sheet ofductile material having a focus hinge that couples two legs, where oneor both of the legs includes a fiber gripping channel (e.g., a V-type,channel type or U-type groove 547 or a mixture of groove shapes) tooptimize clamping forces for a conventional glass optical fiber receivedtherein. In one exemplary embodiment, the element typically has oneV-groove in one leg and a channel groove in the second leg to yield athree line contact region. The ductile material, for example, can bealuminum or anodized aluminum. Gripping device 540 allows a fieldtechnician to grip the optical fiber being terminated remotely from theferrule. Alternatively, gripping device 540 can include a wedge-actuatedmechanical gripping element.

Cap 544 can be configured to engage the gripping element 542 such thatthe element 542 grips the field fiber inserted therein. The cap can beformed or molded from a polymer material, although metal and othersuitable materials can also be utilized. In a preferred aspect, the cap544 can be formed from a material being the same as the material formingthe element 542. Alternatively, a material having at least a similarcoefficient of thermal expansion (CTE) as the element can be utilized.Also, the cap's size is designed to freely fit within housing portion523 such that when it has fully engaged the element, the cap is notrestricted from axial expansion/contraction with the element 542 duringthermal expansion or contraction.

Connector 500 also includes a buffer clamping portion 526 of the collarbody that can be configured to clamp the buffer portion of the opticalfiber cable 515. In one aspect, buffer clamping portion 526 can beconfigured to include a buffer clamp as an integral part of itsstructure. According to an exemplary aspect, buffer clamping portion 526can be configured to clamp a standard optical fiber buffer cladding. Toactivate the particular buffer clamping element, connector 500 canfurther include an actuation sleeve 560 having an opening extendingtherethrough that is axially slidably received by the outer surface ofbuffer clamping portion 526. Moreover, to prevent sharp fiber bends atthe connector/fiber interface, a boot 580 can be utilized.

During connection, the structure of connector 500 can provide a safetyinterlock such that the fiber joint between the stub fiber and the fieldfiber is optically decoupled when the connector is not in use. In moredetail, FIGS. 23-25 show a cross section view of exemplary connector 500before and after mating with a second connector (represented forsimplicity purposes by ferrule 590).

The field fiber end can be prepared by e.g., cutting, stripping, andcleaving (flat or angled). The prepared fiber end is then inserted intothe collar body/housing, through an unactuated gripping device. Theterminal end of the field fiber is positioned proximate to, but not incontact with the second end of the fiber stub (e.g., 117, 217). Theactuating cap 544 of the gripping element can be pressed down onto thegripping element 542 (e.g., 142, 242) to actuate the gripping of thefield fiber. In addition, in an alternative aspect, ferrule 532 can beconfigured similar to either ferrule 314 or ferrule 414 described abovesuch that the abutting end faces of the fibers can be cleaned and/orpolished prior to optical connection (either initial connection orsubsequent connection) through the use of a polishing or cleaning strip.Also, when the field fiber is inserted though the gripping device intothe ferrule, the terminal end may contact the cleaning or polishingstrip. An air gap between the stub fiber 504 and field fiber 505 (ofbetween about 0.005″ to about 0.060″, corresponding to the thickness ofthe cleaning/polishing strip) can be established to optically decouplethe fibers until the connector 500 is mated in a receptacle.

Prior to mating, gripping element 540 is substantially secured withinthe collar body 520. The connectors are first mated as depicted in FIG.24, where ferrule 590 of the second connector contacts ferrule 532 ofconnector 500 at an interface 592. At this contact interface, stub fiber504 of the first connector and a fiber 506 of the second connector arealso placed in contact. Spring 555 of connector 500 preloads a suitableforce onto the connector body.

In FIG. 25, the ferrules 532 and 590 are brought into full contactforce, with the tips of fibers 504 and 506 remaining flush with theirrespective ferrule end faces. Some of the contact force is applied byfiber 506 to the end face of the stub fiber 504. The remaining force ofthe mating presses onto ferrule 532, where part of the force applied tothe ferrule 532 is transferred to the sidewalls 527 of the collar body520, which bow outward in the direction of arrows 587. In addition,spring 555 will be compressed. Further, the ferrule 532 is translatedslightly backward, bringing the second end of stub fiber 504 intocontact with field fiber 505, thus providing a full optical coupling.When the two connectors are un-mated, a gap is re-formed between fibers504 and 505, thus preventing substantial transmission of light throughthe connector 500.

As mentioned above, the exemplary embodiments described herein providean optical connector having a mechanism that can provide for a fieldterminated optical connector. The optical connectors described above canbe used in many conventional optical connector applications such as dropcables and/or jumpers. The optical connectors described above can alsobe utilized for termination (connectorization) of optical fibers forinterconnection and cross connection in optical fiber networks inside afiber distribution unit at an equipment room or a wall mount patchpanel, inside pedestals, cross connect cabinets or closures or insideoutlets in premises for optical fiber structured cabling applications.The optical connectors described above can also be used in terminationof optical fiber in optical equipment. In addition, one or more of theoptical connectors described above can be utilized in alternativeapplications. Moreover, the connectors described above are designed tobe more insensitive to temperature changes and thus can be utilized in alarger range of applications, such as outside plant applications.

Various modifications, equivalent processes, as well as numerousstructures to which the present invention may be applicable will bereadily apparent to those of skill in the art to which the presentinvention is directed upon review of the present specification.

1. An optical fiber connector, comprising: an outer housing; a collarbody disposed in the outer housing, wherein the collar body receives andsecures a ferrule in a first portion of the collar body, wherein theferrule includes a central bore that defines an axis, the ferrulefurther having a fiber stub disposed in a portion of the central bore,the fiber stub comprising a first optical fiber having a first endproximate to an end face of the ferrule and a prepared second endterminating within the ferrule, wherein the collar body further includesa second portion that includes a housing portion to house a grippingdevice that grips a second optical fiber.
 2. The optical fiber connectorof claim 1, wherein the gripping device provides a contact force that isapplied to the second optical fiber in an axial direction and providesoptical contact with the second end of the first fiber inside thecentral bore.
 3. The optical fiber connector of claim 2, wherein thegripping device includes a gripping element and an actuating capconfigured to engage the gripping element to secure a second opticalfiber disposed therein.
 4. The optical fiber connector of claim 3,wherein the gripping element comprises a ductile material having a focushinge that couples two element legs, wherein the actuating cap includesa cam portion formed on a cap leg that engages a rear portion of collarbody upon actuation, wherein each of the legs further includes slotsformed at different axial positions and oriented transverse to the axis,and wherein the gripping element further includes one or moreprojections located on opposite longitudinal end portions of the legs,wherein, upon actuation of the actuating cap, a first projectioncontacts a rear portion of the ferrule and a second projection contactsa portion of the actuating cap.
 5. The optical fiber connector of claim4, wherein contact force is from about 0.1 lbs. to about 0.4 lbs.
 6. Theoptical fiber connector of claim 3, wherein the actuating cap includes acover portion and a main body portion that includes two main legs andtwo spring legs, wherein the main legs include cams disposed on innersurfaces thereof to engage and clamp the element about the secondoptical fiber when the cap is pressed onto the element during actuation,wherein the main legs each include a forward shoulder portion to engagewith a retaining wall portion of the collar body disposed between thegripping element and the ferrule, and wherein, during actuation, thespring legs engage with a cam surface of an opposite portion of thecollar body.
 7. The optical fiber connector of claim 1, wherein theferrule includes a cut-out portion positioned at a generally midpointaxial location of the ferrule that provides a location to apply anadhesive to the central bore at a first portion of the ferrule.
 8. Theoptical fiber connector of claim 1, wherein the ferrule includes a slotformed generally transverse to the axis that receives at least one of acleaning material and a polishing material that is applicable at leastone of to the second end of the first fiber and an abutting end of thesecond fiber.
 9. The optical fiber connector of claim 8, wherein theslot is oriented at an angle of about 5°-about 10° from normal to theaxis.
 10. The optical fiber connector of claim 1, wherein the ferruleincludes a through-hole intersecting and formed generally transverse tothe central bore that receives at least one of a cleaning material and apolishing material that is applicable to at least one of the second endof the first fiber and an abutting end of the second fiber.
 11. Theoptical fiber connector of claim 1, further comprising a cable holdingmember that includes a cable clamping mechanism disposable therein. 12.The optical fiber connector of claim 11, wherein the cable holdingmember further includes a main body and a retention clip, wherein theretention clip is configured to engage a portion of the main body of thecable holding member and secure the clamping mechanism, wherein theclamping mechanism includes a receptive groove formed therein havingengaging projections configured to securely retain the outer portion ofa fiber cable that houses the second optical fiber.
 13. The opticalfiber connector of claim 1, wherein the connector is configured as oneof a plug-type connector and a socket-type connector.
 14. The opticalfiber connector of claim 1, wherein the outer housing is configured tomate with a receptacle.
 15. An optical fiber connector, comprising: anouter housing; and a collar body disposed in the outer housing, whereinthe collar body includes a flexible wall portion, wherein the collarbody receives and secures a ferrule in a first portion of the collarbody, wherein the ferrule includes a central bore that defines an axis,the ferrule further having a fiber stub disposed in a portion of thecentral bore, the fiber stub comprising a first optical fiber having afirst end proximate to an end face of the ferrule and a prepared secondend terminating within the ferrule, wherein the collar body furtherincludes a second portion that includes a housing portion to house agripping device that grips a second optical fiber, wherein the first andsecond fibers are optically coupled upon connection of the optical fiberconnector to one of a connector coupling, a connector adapter and aconnector socket.
 16. The optical fiber connector of claim 15, whereinthe flexible wall portion of the collar body comprises bowed outer sidewalls.
 17. The optical fiber connector of claim 15, wherein the flexiblewall portion of the collar body comprises a resilient material forming aportion of the side walls.
 18. The optical fiber connector of claim 15,wherein the connector is configured as one of a plug-type connector anda socket-type connector.
 19. The optical fiber connector of claim 15,wherein the outer housing is configured to mate with a receptacle.